Abstract

After several years fighting in defence of Mendelian genetics, William Bateson was appointed Director of the John Innes Horticultural Institution in 1910, where he investigated the development of plant chimeras. Recent scholarship has portrayed this research as something of a misstep by Bateson, which left him out of touch with modern developments in biology, including the chromosome theory of heredity. This paper argues that Bateson’s interest in plant chimeras was partly an attempt to address a longstanding controversy in the annals of natural history: the existence, or non-existence, of graft hybrids. Previously unpublished correspondence between Bateson and the German botanist Erwin Baur reveals that Bateson sought to expose graft hybrids as chimeras in order to preserve Weismann’s distinction between somatic and germ cells. For his part, Baur helped Bateson to grasp the true nature of plant chimeras and sent him specimens to display at the Royal Society. The timing of this exchange is significant. In Germany, a former debunker of the graft hybrid hypothesis, botanist Hans Winkler, claimed to have created a genuine botanical graft hybrid. In the United States, leading Mendelian William Castle was engaged in a heated exchange with physiologist Charles Guthrie over the existence of animal graft hybrids. Castle portrayed this clash as an attempt by neo-Lamarckians to overthrow both Weismann and Mendel. This wider context revises our picture of Bateson’s interest in plant chimeras from that of a scientific misstep to a necessary effort to tackle an immediate threat to the future of Mendelian genetics.